This invention relates generally to injection molding and more particularly to valve gated apparatus having a valve member sealing bushing with a thin collar portion which forms a seal against melt leakage.
Valve gated injection molding systems having a valve member sealing bushing are well known. In fact, the applicant's U.S. Pat. No. 4,433,969 which issued Feb. 28, 1984 shows a sealing bushing with a collar portion which extends rearwardly into the manifold to lengthen the sealing contact between the valve member and the sealing bushing. However, in this previous configuration the bushing is located between the manifold and the nozzle which has the disadvantage that additional mold height is required. The applicant's U.S. Pat. No. 4,521,179 which issued Jun. 4, 1985 has the bushing seated in the nozzle which has the disadvantage of being more costly to manufacture. U.S. Pat. No. 4,740,151 to Schmidt et al. which issued Apr. 26, 1988 shows a sealing and retaining bushing which extends rearwardly from the manifold to lengthen the sealing contact. With the demand for more and more compact molds, it is very desirable that the sealing contact between the sealing bushing and the valve member be as long as possible while the height Of the mold is as short as possible. Furthermore, none of these previous arrangements are able to utilize the pressure of the melt to improve the seal of the sealing bushing around the reciprocating valve member.